Electro-optical system



vAug. l, 1939. A. M. SKELLETT ELECTED-OPTICAL SYSTEM Filed Dec; 24, 1956ATTORNEY Patented Aug. 1.1939

'Bell Telephone Laboratories,

Incorporated,

New York, N. Y.,- a corporation of New York Application December 24,1936, Serial No. 117,522

g 10 Claims.

This invention relates to electro-optical systems and more particularlyto the electrographic ing images from currents produced by moving astylus over the subject along selected paths such as the boundary linesbetween areas of distinctlve tone values. The frequency band requiredfor' the transmission of these images is small compared with the bandrequired in ordinary television systems. The present invention isdirected to the improvement of'apparatus of the electrograph type fortransmiting animated images and particularly to an improved apparatusfor transcribing the movements of a stylus along the boundaries ofdistinctive areas of the subject into tracks on a film or other recordmember for use particularly with animated carto'ons or similar sketches.

It is another object of this invention to provide an improvedtranscribing device for animated subjects. r

It is a further object of this invention to providea novel transparenttemplate to assist in tracing the background of the subject field.

In accordance with one embodiment of this invention, shown for purposesof. illustration and hereinafter described in detail, the images ofindividual, frames of an animated film are projected upon a ground glassscreen The boundaries of distinctive areas of the image figure on thescreen are then traced by a stylus and as the stylus moves around in thefield two cables attached to it open two slits in a light valve inproportion to the rectangular coordinates of its successive positionswith respect to a pairof oo- The dimension of the track along the filmrepresents the length of time taken to trace a particular portion of theimage and may be used tocontrol variations in density of the receivedimage.*- A transparent template with a continuous groove tofit over andcoincide with the background may be. mounted so as-to be quickly swungin position on the ground glass and, with ,itthe background-may betranscribed at a speed greater than that of the central figure. As soonas one frame is transcribed, another frame is shifted into place in theprojector and the transcribing process repeated. For reproducing orconverting the tracks on the film into signal currents, the images ofthe tracks on the film are projeced upon two photocells. These cells maybe connected respectively through'amplifiers to the two pairs ofdeflecting plates of a cathode ray receiver.

The invention will be' more readily understood by referring to thefollowing description, taken in connection with the accompanying drawingforming a part thereof in which:

Fig. 1 is a schematic diagram of an electrographic systemembodying thisinvention;

Fig. 2 is a perspective view of the transcriber;

Fig. 3 is a top view of a transparent template used in the arrangementof Fig. 2;

Fig. 4 is a cross-sectional view of the template of Fig. 3; and p Fig. 5'is an enlarged diagrammatic'showing of. the optical system of Fig. 2. v

Referring more particularly to the drawing, Fig. 1 shows schematicallyan electrograph sys- .tem embodying this invention. In this figuresketches III, which may be views of the same After proper developmentand, if 'desired,'

fixing, the film I2 is passed into a device I6 which is called aconverter. If desired there may be a time interval between thetranscribing and converting operations. In other" words, the tracks l4and'l5 on the film 12 may be made well in,

advance of the time the program is transmitted or broadcast; In theconverter IS, the tracks on the film are used to generate signalcurrents which are transmitted to a receiving station which preferablyincludes a cathode ray device I I. The converter preferably comprises apair of photocells actuated by the images of the tracks I4 and IS on thefilm ii to produce varying signal currents respectively proportional tothe suc-' cessive positions of the stylus with respect to the pair ofcoordinate axes. Fora more complete description .of a converting devicesomewhat similar to the device l6, reference may be made to theabove-mentioned Skellett application.

The signal currents generated by the photoelectric cells in theconverter It may then be used to modulate carrier waves generated bysuitable oscillators (not shown) and these modulated carrier waves aretransmitted over respective channels l8 and [9, which may be either lineor radio channels, to the receiving station R. Suitable amplifyingdevices 20 and 2| may be used at the transmitting station and amplifyingdevices 22 and 23 at the receiving station to produce greatly amplifiedsignals.

The signals in channels l8 and I9 are then applied to two pairs ofdeflecting plates 24 and 25 of the cathode ray receiving tube l'l.Cathode ray tube I1 comprises suitable means (not shown) for producing abeam of electrons and for accelerating this beam towards a fluorescentscreen 26. The voltages from the channels |8and l9, respectivelyproportional to the'signal currents generated at the transmittingstation, create electrostatic fields between the members of pairs ofdeflecting plates 24 and 25 respectively which deflect the beam topositions corresponding to the changing locations of the stylus at thetransmitting station. If desired, means may be provided for generating asignal when the stylus is lifted from the surface of the representation(as when it is moved from one boundary to another) and this signal usedto cut off the cathode ray beam .of the tube I'I during this interval oftime. For a description of apparatus for producingthis signal togetherwith a morecomplete description of the system shown in Fig. 1 on theright of the transcribing device I l, reference may be made to theabove-mentioned Skellett application. If desired, the stylus may bemoved quickly from one boundary to another and this will show on theimage at the receiving station only as a faint trace.

The improved transcribing device of this invention for making tracks onfilm corresponding to the successive positions of the stylus withrespect to a pair of coordinate axes is shown in Fig. 2, the arrangementbeing particularly applicable to animated cartoons or similar subjects.In this arrangement, a projecting apparatus 30 is arranged to projectupon a ground glass screen 3 I,

one frame at a time, the images of the frames of a motion picture filmwhich may be, for example, of the type generally known as animatedcartoons. A stylus 32 traces boundaries of the distinctive areas of theimage 33, preferably in a continuous line, and the motions of the stylus32 operate the opening and closing of a double light valve 34 by meansof appropriate cables 35 and 36 passing over reels 31 and 38 andattached to moving slide members 39 and 40. The slide members 39 and 40,acting against the pressure of springs 4| and 42, control the size ofthe slits 44 in accordance with the position of the stylus with respectto its coordinate axes. -A- point 0 represents the intersection of the Xand Y axes. A table or other supporting device 53 supports the screen 3|and it maybe provided with arms 54 and 55 to support the reels 31 and38.

Light from a suitable elongated source 45 is focused byany suitabledevice, such as a cylindrical lens 46, upon or near the plane of slits'44, and the image of these slitsis formed on film I 2 by means ofsuitable lenses 4! and 48 to produce variable widthimage tracks l4 andI5 The film I2 is adapted to move continuously in the direction of thearrow by means of suitable rollers 49, 50, 5| and 52. If it is desiredto make all the boundaries of the same density, the stylus is movedalong theboundaries at a uniform rate of speed. Shading can beaccomplished by varying this rate ofspeed. After the film l2 has beendeveloped, fixed and dried in accordance with well-known photographictechnique, the tracks on the film may be used to generate the signalcurrentsfor transmission to the receiving station as stated above inconnection with Fig. 1.

' It is estimated that a skilled operator will spend no more time intranscribing the drawing than was required by the artist in drawing itoriginally. As there are time-saving tricks peculiar to-the art ofproducing animated cartoons so there are also such artifices peculiar tothis transcription technique which will save time and laborconsiderably. When one frame has been completely traced, the next frameis imaged by means of the projector 30 upon the ground glass screen 3|and this image traced by the stylus as described above.

When the image of every frame has been traced by the stylus, the film I2will comprise a coordinate track record of the entire moving picturefilm used in the projector 30. Regardless of the time taken totranscribe the images on a film from the projector 30 into tracks on thefilm I2, the film I2 is run past the photoelectric cells in theconverter device l6 at a speed such that a continuous animated image .isproduced on the fluorescent screen 26 of the cathode ray tube I1 at thereceiving station. For example, film l2 may be run through the converterat a speed such that twenty-four complete frames are produced per secondin the cathode ray tube l1. Since this period of time is within theperiod of persistence of vision, the image on the screen 26 will movewithout flicker effect.

Various changes may be made in the transcribing device of Fig- 2. Thestylus may be coupled to the light valve by any other suitable means,either mechanical or electrical.- As an example of an electrical methodfor coupling the movement of-the stylus in the light valve, refercation.The film I2 may be replaced by any other record member,v such as forexample magnetic tape, or a sound record on wax or metal. If any ofthese other record members are used, the associated recording apparatuswould be used in place of the light valve 34.

Frequently in transcribing animated cartoons, the background remains thesame for a considerable number of pictures. The transcribing of thebackground may be simplified by the use of a suitable device such as thetransparent template disclosed in Figs. 3 and 4. This template 60comprisesa flat plate having a continuous groove 6| cut therein in theshape of the background. The stylus 32 is adapted to move in this grooveand hence the background may be quickly and easily transcribed. Thedensity of the background line on the fluorescent screen 26 may becontrolled by I than those of the ordinary high fidelity radioaice'p-is' 5 the speed at which the stylusismoved in the groove ii. Ifit is traced quickly the line will be light whereas if the stylus ismoved at a slower rate of speed, the background line will be relativelydark. As explained above, thissame general principle applies to thefigureas well as to the background. A transcriber artist may use thisprinciple to produce shaded images.

\ The frequency band width'required by the system of this invention isrelatively small compared with that required in ordinary televisionsystems. It is inherent in well known systems in television that highdefinition must at all times be realized no matter how simple thetransmitted image may be. Many useful and entertaining images, however,do not contain a great amount of detail and in transmitting them largeblank areas on the,-

available field are wastefully transmitted. The animated cartoon is anexample of such a simple image. In this invention, the figure and linebackground without the blank areas is transmitted and thus a greatsimplification occurs, which simplification is expressed in the'loweringof the frequency band required for transmission to a width sufiicientso'that it may be used with carriers of the ordinary broadcast frequencyrange. The required band widths are no larger transmitting stations oftoday.

Various modifications may be made in the invention as above disclosed,the scope of which is indicated by the appended claims. In the claims,the expression "boundaries of areas of distinctive tone values isintended to be inclusive of the case where an area of distinctive tonevalue is a line as in an outline sketch or drawing. The two parallelboundaries'of a line area are for practical purposes coincident, so thata stylus tracing the line is in effect tracing each boundary of the linearea; that is, tracing both boundaries of the line area simultaneously.

What is claimed is:

l. A method of image production comprising the steps of projectingsuccessive still images of a subject upon a screen, each image differingfrom its immediately preceding image to an extent corresponding to atime interval within the period of persistence of vision, tracing theboundaries of 1 areas of distinctive tone values of said images,generating two potentials continuously varying in accordancewith thepositions of the successively traced elements of said boundaries withrespect to the axes of a coordinate system, recordingsaid potentials,and producing electric signal currents in accordance with said recordedpotentials at a rate of speed different from that at which saidpotentials were recorded.

2. A method for making a coordinate recordmember corresponding tosuccessive images of an animated subject which comprises projectingsuccessive images of the subject upon a screen, each image diiferingfrom its immediately preceding image to an extent corresponding to atime interval within the period of persistence of vision, tracing theboundaries of areas of distinctive tone values of each image on thescreen, and utilizing the positions of the successively traced elementsof said boundaries with. respect to a pair of coordinate axes to producea record inember of said positions. I

- 3. A system of image production for animated subjects comprising ascreen, means for projectingasuccession of still images of the subjecton said screen, each image differing from its immediately precedingimage to an extent correspond- 3 mg to a-time' interval within theperiodor aries of areas of'distlnctive tone values of each image insuccession, and means for recording as tracks one record member themovement of said styluswith respect to a pair of coordinate axes.

4.;A system of image production for animated subjects comprising ascreen, means for successively projecting still images oflthe subject onsaid screen, each image differing from its immediately preceding imageto an extent corresponding to a time interval within the period of per-'sistence of vision, a stylus for tracing the bound- P sistence of'vision, a stylusfor tracing the boundaxles of areas of distinctive tonevalues of each image in succession, a light source, a moving film, and apair of light apertures located between-sald light source and said film,the widths of which are respectively controlled by the movement of saidstylus with respect to coordinate axes perpendicular to each other,whereby there is recorded on said film tracks correspondingrespectivelyito" the successive positions of the stylus with respect tosaid system of coordinates 4 r 5-. In combination, a motion picture filmrec- 0rd of an animated subject, a screen, means for projecting, a frameat a time, images of said animated subject upon said screen, each frameimage diifering from its immediately preceding frame image to an extentcorresponding to a time interval within the period of persistence ofvision, means for tracing witha stylus the boundareas of' distinctivetone values of each of said images, and means for making a record memberof the movements of said tracing means with respect to a system ofcoordinates.

7. An electrograph system comprising a. transparent screen, means forprojecting a series of images of an animated subject on, one side ofsaid screen, each of said images differing from its immediatelypreceding image in the series to an extent corresponding to a timeinterval within the persistence of vision and each image comprising abackground which is substantially the same as the background in theother images in the series, a transparent template having a continuousgroove therein which fits over and coincides with the background in eachof said images, said transparent template being placed on the side ofsaid screen remote from the side upon which the images are projected, astylus, and means for mounting said stylus so that it may be quicklymoved'in said groove.

8. A'system of image production for animated .subjectscomprising meansfor successively projecting an image of each frame of a film record ofan animated subject upon a screen, each frame image differing from .itsimmediately preceding frame image to an extent corresponding to a timeinterval within the period of persistence of vision, stylus controlledmeans for resolving the image of each frame into two signal currentsrescreen, a supporting member for said screen,

means for successively projecting an image of each frame of a filmrecord of an animated subject upon said screen, each frame imagediffering from its immediately preceding frame image to an extentcorresponding to a time interval within the period of persistence ofvision, a stylus for tracing the boundaries of areas of distinctive tonevalues of'each frame image, a light valve having two apertures therein,means controlled by the movement of said stylus for de-,

termining the width of said apertures, a light source, means forfocusing the light from said light source upon said apertures, a movingfilm, and means for focusing the light passing through said aperturesupon said moving film to make tracks thereon corresponding respectivelyto the successive positions of said stylus with respect to a pair ofcoordinate axes. 1

10. In combination, a supporting member, said supporting member having atransparent portion therein, said transparent portion being arranged tohave projected thereon a succession of still images, each imagediffering from its immediately preceding image to an extentcorresponding to a time interval within the period of persistence ofvision, an elongated plate member having two elongated slits therein, anelongated light source, means for focussing radiations from saidelongated light source upon said elongated slits, a stylus, means forsupporting said stylus so that as it moves over boundaries of areas ofdistinctive tone values of an image on said transparent portions of saidsupporting member portions of said elongated slits are covered so thatlight from said source does not reach said slits, and a record memberfor receivingthe light which passes through the parts of said elongatedslits which are not obscured, whereby a record is made of thecoordinates of the successive positions of said moving styluswith'respect to a pair of coordinate axes in a time interval muchgreater than one within the period of persistence of vision.

ALBERT M. SKEILE'I'I;

